Wave tank 3b:
30m by 25m, 1 meter water depth
Flat bottom
Wavemaker sets velocity at left boundary to:
    u(0,y,t) = 0.2*sin(4*t1) + 0.2*sin(4*t2)
where
    t1 = max(t - .05*(30-y), 0),
    t2 = max(t - .05*y, 0).
Computed on 125x150 grid Some frames: